what happen in chapter 39?

They were ready to open the interior of the Earth with gunpowder. They move away on the raft before the ignite the explosion. Then Axel describes,

"Beyond the rock which had been blown up, there existed a mighty abyss. The explosion had caused a kind of earthquake in this soil, broken by fissures and rents. The gulf, thus suddenly thrown open, was about to swallow the inland sea which, transformed into a mighty torrent, was dragging us with it."

They were now lost. They moved along the current very quickly and lost much of their cargo. The raft goes faster. THe raft is jolted back on to course.